Repair 3 and amyloidosis Dr Heyam awad FRCPath

wound healing 1. first intention 2. second intention

wound healing Healing by first intention (primary union) - healing of a clean, uninfected surgical incision approximated by surgical sutures - focal disruption of epithelial basement membrane continuity so.. A small scar is formed, with minimal wound contraction - epithelial regeneration is the principal mechanism of repair

Healing by second intention or second Union - tissue loss is extensive, e:g in large wounds, abscess, or ulceration - The repair process is more complex and involves a combination of regeneration and scarring.

Healing by secondary union is characterized by 1. Intense inflammation 2.Abundant granulation tissue, 3. Formation of a large scar, 4. wound contraction mediated by myofibroblasts

Wound contraction Within 6 weeks, large skin defects may be reduced to 5% to 10% of their original size.

Wound strength -sutured wounds= 70% of normal skin strngth due to the sutures. -At 1 week (sutures removed).. 10% of normal. - strength then increases as a result of collagen synthesis exceeding degradation during the first 2 months and by structural modification of collagen. - maximum strength reached: 70% to 80% of normal by 3 months.

amyloidosis a condition associated with a number of inherited, neoplastic and inflammatory disorders.

-deposition of extracellular fibrillar proteins -These abnormal fibrils are produced by the aggregation of misfolded proteins (which are soluble in their normal folded configuration).

-Amyloid is deposited in the extracellular space in various tissues and organs of the body -These fibillary proteins are responsible for tissue damage and functional compromise

Amyloid stained by Congo red under light microscope

Amyloid stained by Congo red under polarizing microscope

Congo red stain

By electron microscope -All types of amyloid consist of continuous, non-branching fibrils with a diameter of approximately 7.5 to 10nm. With a cross- β-pleated sheet conformation

Chemical Properties of Amyloid Proteins -Amyloid is not a single chemical entity. -Primary and secondary amyloidosis.